Wire drawing apparatus



'Feb- 20, 1968 T. c. MCGEARY ETAL 3,

WIRE DRAWING APPARATUS Original Filed Nov. 2, 196

VENTORS THOMAISNC. McGEARY LEWIS M.COWDEN ATTORNE United States PatentWIRE DRAWING APPARATUS Thomas C. McGeary and Lewis M. Cowden,Indianapolis, Ind., assignors to Union Carbide Corporation, acorporation of New York Continuation of abandoned application Ser. No.408,279, Nov. 2, 1964. This application Mar. 13, 1967, Ser. No. 622,826Claims. (Cl. 72289) This invention relates to wire drawing apparatus,and more particularly, to wire contact members, such as draw blocks.

Briefly, the invention provides a wire drawing apparatus comprising, forexample, a metal draw block having an outer coating of refractorymaterial the minimum thickness of which is 0.010 inch, a hardness ofbetween 800 and 1,300 V.P.N., and a rnicro-lamellar structure.

This application is a continuation of application Ser. No. 408,279,filed Nov. 2, 1964, now abandoned.

In the manufacture of wire, that is, in the drawing of wire down to itsrequired size, draw blocks are used to pull the wire through the dies.Such draw blocks, or as they are sometimes called, capstans, undergosevere wear and abrasion. Such wear, caused by the thin ware travelingat high speed, forms thin grooves in the surface which lead to jammingand breaking of the wire strands. In addition to the wear problem, thereis also a corrosion problem due to the lubricant being used in thedrawing operation.

Prior to this invention, wire drawing blocks primarily consisted offlame hardened cast iron. Normal service life with such draw blocksamounted to about six months. Of recent years attempts have been made toincrease the life of draw blocks by applying a wear resistant coating tothe wear surface. A hard wear resistant bonded tungsten carbide coatinghas been used, for example. Whilesuch coating measureably increased thelife of the draw blocks, it still has not met the heavy demands of theindustry.

It is, therefore, the principal object of the present invention toprovide an improved wire contact member for wire drawing machines, whichwill give a longer service life than has been possible in the past.

FIGURE 1 is a plan view of an example of wire drawing apparatusincorporating the invention;

FIGURE 2 is an enlarged view in side elevation of the draw block;

FIGURE 3 is a view similar to FIGURE 1 of a modification of theinvention;

FIGURE 4 is an enlarged perspective view in cross section of one of thedraw blocks shown in FIGURE 3; and

FIGURE 5 is a fragmentary enlarged view in cross section of a portion ofthe block shown in FIGURE 2.

With reference to FIGURE 1, there is depicted a draw block 14 for onetype of wire drawing operation. Wire is drawn from a supply reel 11through a die 12 by a draw block 14 driven by a motor 15, FIGURE 2. Fromthere the wire 10 is fed to and wound on a reel 16. The function of thedraw block 14 is to pull the wire 10 through the preceding die 12. Inthis type of operation a straight frusto-conically faced draw block 14is used. The wire 10 climbs up the tapered face 13 of the block 14, asshown.

Another type of wire drawing operation is schematically shown in FIGURE3. In this system, the wire 10 is pulled through separate dies encasedin housing 32 by stepped draw blocks 30. The wire is pulled from step 1through a die to step 1a, then from step 111 through another die to step2, and so on. In this system, each draw block 30 is not only stepped,but each step is grooved at 34 as shown in FIGURE 4.

3,369,386 Patented Feb. 20, 1968 Such pulling of the wire by the drawblocks in both systems, presents a severe wear problem, especially whenthe speed with which the wire is traveling over the blocks isconsidered, such speed being as high as 5000 ft./min.

According to the invention, the outer surface of the draw blocks 14 and34 are provided with a novel coating 18, FIGURE 5, composed ofrefractory material selected from the class consisting of chrome oxide,and ferrochrome-tungsten carbide alloy. More particularly, powder of theselected material is passed through an arc torch in the manner describedin US. 3,016,447 and then, for example, projected onto a base, which inthe case of the present invention would be the outer surface of the wirecontact member. Because of the torchs constricting nozzle, the arcbecomes well stabilized thus yielding an intense columnar plasma. Thetorch itself operates in a nontransferred mode. Coatings formedaccording to this arc process have a dense, micro-lamellar structurewith bonded, overlapping leaves.

As stated previously, prior art drawing blocks were either flamehardened, or their wear surfaces were coated with bonded tungstencarbide. Flame hardened draw blocks have a Vickers hardness number ofabout 1400. Thus, the increase in draw block life that was achieved bythe use of bonded tungsten carbide coatings was to be ex pected.However, it has been quite unexpectedly found that even though thechrome oxide coating of the invention has a lower Vickers hardness ofabout 1300, an even longer draw block life can be achieved. In the caseof the ferrochrome-tungsten carbide alloy coating of the invention, theVickers hardness number is even lower, i.e. 850 to 950 with a usefullife of over 14 months.

The following table indicates the wear life of wire draw blocks havingwear surface coatings of chrome oxide and ferrochrome-tungsten carbidealloy by the described are torch process, compared with prior art typesof wear surfaces.

A carbon steel draw block of the type described with reference to FIGURE2 was coated. The draw block had a height of about 5" and an CD. of 20".The torch was held about to 1 inch away from the coating surface. Thedraw block was rotated at about 300 rpm. Argon gas was fed through thetorch at the rat-e of about 300 c.f.h. Powdered chrome oxide was fedthrough the torch with the aid of argon gas at the rate of 50-60 gms.per min. The substrate was cooled with carbon dioxide. A coating about.010 inch thick was obtained.

Example 2 Five nine-step, carbon steel draw blocks of the type shown inFIGURE 4 were coated by the same process. The blocks had a 10 inch O.D.at the top. The grooves were inch deep by about /2 inch wide. Argon gaswas fed through the torch along with the chromia powder which was alsocarried by argon. The blocks were cooled with carbon dioxide. CoatingWas achieved three steps at a time, starting with the step at thelargest diameter. The torch standoff was maintained at about 1 /2 inchesin all cases. During the first six steps the draw blocks were ro- 3lated at about 760 r.p.m., during the last three steps, at 2080 r.p.m.The coating thickness varied from .010 to .014 inch.

After the draw blocks were coated, they were finished by one of threeprocedures depending upon the size of the wire to be drawn: sanding,grinding, or grinding and lapping. For example, for a inch wire, thesurface was sanded only. While for a .010 inch Wire, the surface wasground and lapped.

The preferred ferrochrorne-tungsten carbide alloy is disclosed in theapplication of Ronald H. Rath, Ser. No. 336,353, filed Jan. 8, 1964, forWear and Corrosion Resistant Coating.

Example 3 A carbon steel draw block of the type described with referenceto FIGURE 2 was coated with an arc torch by the process described. Thedraw block had a height of about 12" and an OD. of 24". The torch washeld about to inch away from the coating surface. The drawblock wasrotated at about 340 r.p.m. Argon gas and nitrogen gas Were fed throughthe torch at the rate of about 330 c.f.h. Powdered 40% ferrochrome-60%tun-gsten carbide powder was fed through the torch with the aid of argongas at the rate of 68 grams per min. A coating about .011 inch thick wasobtained.

We claim:

1. Wire drawing apparatus comprising a metal draw block having an outercoating of refractory material the minimum thickness of which is 0.010inch, a hardness of of between 850 and 1,300 V.P.N., and amicro-lamellar structure.

2. Wire drawing apparatus as defined by claim 1, in which the refractorycoating material is selected from the class consisting of chromia andferrochrome tungsten carbide alloy.

3. A wire draw block composed of steel having a wire contacting surfacecoating consisting of chromia.

4. A wire draw block composed of steel having a Wire contacting surfacecoating consistnig of ferrochrometungsten carbide alloy.

5. Wire drawing apparatus comprising a member provided with a coatingadapted for contact with moving wire, said member being composed ofmetal and the coating thereon being composed of a lamellar structure ofrefractory material selected from the class consisting of chromia and aferrochrome-tungsten alloy.

References Cited UNITED STATES PATENTS 2,025,535 12/1935 Sommer 724l9CHARLES W. LANHAM, Primary Examiner.

H. D. HOINKES, Assistant Examiner.

1. WIRE DRAWING APPARATUS COMPRISING A METAL DRAW BLOCK HAVING AN OUTERCOATING OF REFRACTORY MATERIAL THE MINIMUM THICKNESS OF WHICH IS 0.010INCH, A HARDNESS OF OF BETWEEN 850 AND 1,300 V.P.N., AND AMICRO-LAMELLAR STRUCTURE.